1. Field of the Invention
In one aspect, the invention provides new methods for manufacture ceramic resistive igniter elements that include injection molding of one or more regions of the formed element. Igniter elements also are provided obtainable from fabrication methods of the invention are provided.
2. Background
Ceramic materials have enjoyed great success as igniters in e.g. gas-fired furnaces, stoves and clothes dryers. Ceramic igniter production includes constructing an electrical circuit through a ceramic component a portion of which is highly resistive and rises in temperature when electrified by a wire lead. See, for instance, U.S. Pat. Nos. 6,582,629; 6,278,087; 6,028,292; 5,801,361; 5,786,565; 5,405,237; and 5,191,508.
Typical igniters have been generally rectangular-shaped elements with a highly resistive “hot zone” at the igniter tip with one or more conductive “cold zones” providing to the hot zone from the opposing igniter end. One currently available igniter, the Mini-Igniter™, available from Norton Igniter Products of Milford, N.H., is designed for 12 volt through 120 volt applications and has a composition comprising aluminum nitride (“AlN”), molybdenum disilicide (“MoSi2”), and silicon carbide (“SiC”).
Igniter fabrication methods have included batch-type processing where a die is loaded with ceramic compositions of at least two different resistivities. The formed green element is then densified (sintered) at elevated temperature and pressure. See the above-mentioned patents. See also U.S. Pat. No. 6,184,497.
While such fabrication methods can be effective to produce ceramic igniters, batch-type processing presents inherent limitations with respect to output and cost efficiencies.
Current ceramic igniters also have suffered from breakage during use, particularly in environments where impacts may be sustained such as igniters used for gas cooktops and the like.
It thus would be desirable to have new ignition systems. It would be particularly desirable to have new methods for producing ceramic resistive elements. It also would be desirable to have new igniters that have good mechanical integrity.